feat: add android context plugin (#14)

* feat: add android context plugin

android/build.gradle

@@ -40,10 +40,10 @@ android {
 }
 
 dependencies {
-    implementation project(':common')
-    implementation project(':common-android')
-    implementation project(':id')
-    implementation project(':core')
+    api project(':common')
+    api project(':common-android')
+    api project(':id')
+    api project(':core')
     implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.5.2'
     implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.5.2'
 

android/src/main/java/com/amplitude/android/Amplitude.kt

@@ -1,19 +1,154 @@
 package com.amplitude.android
 
+import android.content.Context
+import com.amplitude.android.plugins.AndroidContextPlugin
+import com.amplitude.android.plugins.AndroidLifecyclePlugin
 import com.amplitude.core.Amplitude
+import com.amplitude.core.Storage
 import com.amplitude.core.platform.plugins.AmplitudeDestination
 import com.amplitude.core.utilities.AnalyticsIdentityListener
+import com.amplitude.core.utilities.FileStorage
 import com.amplitude.id.FileIdentityStorageProvider
 import com.amplitude.id.IdentityConfiguration
 import com.amplitude.id.IdentityContainer
+import kotlinx.coroutines.launch
 
 open class Amplitude(
     configuration: Configuration
 ) : Amplitude(configuration) {
 
+    private var inForeground = false
+    var sessionId: Long = -1
+        private set
+    private var lastEventId: Long = -1
+    private var lastEventTime: Long = -1
+    private var previousSessionId: Long = -1
+
     override fun build() {
-        idContainer = IdentityContainer.getInstance(IdentityConfiguration(instanceName = configuration.instanceName, apiKey = configuration.apiKey, identityStorageProvider = FileIdentityStorageProvider()))
+        val storageDirectory = (configuration as Configuration).context.getDir("${FileStorage.STORAGE_PREFIX}-${configuration.instanceName}", Context.MODE_PRIVATE)
+        idContainer = IdentityContainer.getInstance(
+            IdentityConfiguration(
+                instanceName = configuration.instanceName,
+                apiKey = configuration.apiKey,
+                identityStorageProvider = FileIdentityStorageProvider(),
+                storageDirectory = storageDirectory
+            )
+        )
         idContainer.identityManager.addIdentityListener(AnalyticsIdentityListener(store))
+        amplitudeScope.launch(amplitudeDispatcher) {
+            previousSessionId = storage.read(Storage.Constants.PREVIOUS_SESSION_ID) ?.let {
+                it.toLong()
+            } ?: -1
+
+            add(AndroidContextPlugin())
+        }
         add(AmplitudeDestination())
+        add(AndroidLifecyclePlugin())
+    }
+
+    fun onEnterForeground(timestamp: Long) {
+        amplitudeScope.launch(amplitudeDispatcher) {
+            startNewSessionIfNeeded(timestamp)
+            inForeground = true
+        }
+    }
+
+    fun onExitForeground(timestamp: Long) {
+        amplitudeScope.launch(amplitudeDispatcher) {
+            inForeground = false
+            if ((configuration as Configuration).flushEventsOnClose) {
+                flush()
+            }
+            storage.write(Storage.Constants.PREVIOUS_SESSION_ID, sessionId.toString())
+            storage.write(Storage.Constants.LAST_EVENT_TIME, lastEventTime.toString())
+        }
+    }
+
+    fun startNewSessionIfNeeded(timestamp: Long): Boolean {
+        if (inSession()) {
+
+            if (isWithinMinTimeBetweenSessions(timestamp)) {
+                refreshSessionTime(timestamp)
+                return false
+            }
+
+            startNewSession(timestamp)
+            return true
+        }
+
+        // no current session - check for previous session
+        if (isWithinMinTimeBetweenSessions(timestamp)) {
+            if (previousSessionId == -1L) {
+                startNewSession(timestamp)
+                return true
+            }
+
+            // extend previous session
+            setSessionId(previousSessionId)
+            refreshSessionTime(timestamp)
+            return false
+        }
+
+        startNewSession(timestamp)
+        return true
+    }
+
+    private fun setSessionId(timestamp: Long) {
+        sessionId = timestamp
+        previousSessionId = timestamp
+        amplitudeScope.launch(amplitudeDispatcher) {
+            storage.write(Storage.Constants.PREVIOUS_SESSION_ID, timestamp.toString())
+        }
+    }
+
+    private fun startNewSession(timestamp: Long) {
+        // end previous session
+        if ((configuration as Configuration).trackingSessionEvents) {
+            sendSessionEvent(END_SESSION_EVENT)
+        }
+
+        // start new session
+        setSessionId(timestamp)
+        refreshSessionTime(timestamp)
+        if ((configuration as Configuration).trackingSessionEvents) {
+            sendSessionEvent(START_SESSION_EVENT)
+        }
+    }
+
+    private fun sendSessionEvent(sessionEvent: String) {
+        if (!inSession()) {
+            return
+        }
+        track(sessionEvent)
+    }
+
+    fun refreshSessionTime(timestamp: Long) {
+        if (!inSession()) {
+            return
+        }
+        lastEventTime = timestamp
+        amplitudeScope.launch(amplitudeDispatcher) {
+            storage.write(Storage.Constants.LAST_EVENT_TIME, timestamp.toString())
+        }
+    }
+
+    private fun isWithinMinTimeBetweenSessions(timestamp: Long): Boolean {
+        val sessionLimit: Long = (configuration as Configuration).minTimeBetweenSessionsMillis
+        return timestamp - lastEventTime < sessionLimit
+    }
+
+    private fun inSession(): Boolean {
+        return sessionId >= 0
+    }
+
+    companion object {
+        /**
+         * The event type for start session events.
+         */
+        const val START_SESSION_EVENT = "session_start"
+        /**
+         * The event type for end session events.
+         */
+        const val END_SESSION_EVENT = "session_end"
     }
 }

android/src/main/java/com/amplitude/android/Configuration.kt

@@ -10,7 +10,7 @@ import com.amplitude.core.utilities.FileStorageProvider
 
 class Configuration(
     apiKey: String,
-    context: Context,
+    val context: Context,
     flushQueueSize: Int = FLUSH_QUEUE_SIZE,
     flushIntervalMillis: Int = FLUSH_INTERVAL_MILLIS,
     instanceName: String = DEFAULT_INSTANCE,
@@ -19,7 +19,17 @@ class Configuration(
     loggerProvider: LoggerProvider = AndroidLoggerProvider(),
     minIdLength: Int? = null,
     callback: ((BaseEvent) -> Unit)? = null,
-    useAdvertisingIdForDeviceId: Boolean = false,
-    useAppSetIdForDeviceId: Boolean = false,
-    enableCoppaControl: Boolean = false
-) : Configuration(apiKey, flushQueueSize, flushIntervalMillis, instanceName, optOut, storageProvider, loggerProvider, minIdLength, callback)
+    val useAdvertisingIdForDeviceId: Boolean = false,
+    val useAppSetIdForDeviceId: Boolean = false,
+    val newDeviceIdPerInstall: Boolean = false,
+    val trackingOptions: TrackingOptions = TrackingOptions(),
+    val enableCoppaControl: Boolean = false,
+    val locationListening: Boolean = true,
+    val flushEventsOnClose: Boolean = true,
+    val minTimeBetweenSessionsMillis: Long = MIN_TIME_BETWEEN_SESSIONS_MILLIS,
+    val trackingSessionEvents: Boolean = true
+) : Configuration(apiKey, flushQueueSize, flushIntervalMillis, instanceName, optOut, storageProvider, loggerProvider, minIdLength, callback) {
+    companion object {
+        const val MIN_TIME_BETWEEN_SESSIONS_MILLIS: Long = 5 * 60 * 1000
+    }
+}